| 1 | package bytes; |
| 2 | |
| 3 | our $VERSION = '1.02'; |
| 4 | |
| 5 | $bytes::hint_bits = 0x00000008; |
| 6 | |
| 7 | sub import { |
| 8 | $^H |= $bytes::hint_bits; |
| 9 | } |
| 10 | |
| 11 | sub unimport { |
| 12 | $^H &= ~$bytes::hint_bits; |
| 13 | } |
| 14 | |
| 15 | sub AUTOLOAD { |
| 16 | require "bytes_heavy.pl"; |
| 17 | goto &$AUTOLOAD if defined &$AUTOLOAD; |
| 18 | require Carp; |
| 19 | Carp::croak("Undefined subroutine $AUTOLOAD called"); |
| 20 | } |
| 21 | |
| 22 | sub length ($); |
| 23 | sub chr ($); |
| 24 | sub ord ($); |
| 25 | sub substr ($$;$$); |
| 26 | sub index ($$;$); |
| 27 | sub rindex ($$;$); |
| 28 | |
| 29 | 1; |
| 30 | __END__ |
| 31 | |
| 32 | =head1 NAME |
| 33 | |
| 34 | bytes - Perl pragma to force byte semantics rather than character semantics |
| 35 | |
| 36 | =head1 SYNOPSIS |
| 37 | |
| 38 | use bytes; |
| 39 | ... chr(...); # or bytes::chr |
| 40 | ... index(...); # or bytes::index |
| 41 | ... length(...); # or bytes::length |
| 42 | ... ord(...); # or bytes::ord |
| 43 | ... rindex(...); # or bytes::rindex |
| 44 | ... substr(...); # or bytes::substr |
| 45 | no bytes; |
| 46 | |
| 47 | |
| 48 | =head1 DESCRIPTION |
| 49 | |
| 50 | The C<use bytes> pragma disables character semantics for the rest of the |
| 51 | lexical scope in which it appears. C<no bytes> can be used to reverse |
| 52 | the effect of C<use bytes> within the current lexical scope. |
| 53 | |
| 54 | Perl normally assumes character semantics in the presence of character |
| 55 | data (i.e. data that has come from a source that has been marked as |
| 56 | being of a particular character encoding). When C<use bytes> is in |
| 57 | effect, the encoding is temporarily ignored, and each string is treated |
| 58 | as a series of bytes. |
| 59 | |
| 60 | As an example, when Perl sees C<$x = chr(400)>, it encodes the character |
| 61 | in UTF-8 and stores it in $x. Then it is marked as character data, so, |
| 62 | for instance, C<length $x> returns C<1>. However, in the scope of the |
| 63 | C<bytes> pragma, $x is treated as a series of bytes - the bytes that make |
| 64 | up the UTF8 encoding - and C<length $x> returns C<2>: |
| 65 | |
| 66 | $x = chr(400); |
| 67 | print "Length is ", length $x, "\n"; # "Length is 1" |
| 68 | printf "Contents are %vd\n", $x; # "Contents are 400" |
| 69 | { |
| 70 | use bytes; # or "require bytes; bytes::length()" |
| 71 | print "Length is ", length $x, "\n"; # "Length is 2" |
| 72 | printf "Contents are %vd\n", $x; # "Contents are 198.144" |
| 73 | } |
| 74 | |
| 75 | chr(), ord(), substr(), index() and rindex() behave similarly. |
| 76 | |
| 77 | For more on the implications and differences between character |
| 78 | semantics and byte semantics, see L<perluniintro> and L<perlunicode>. |
| 79 | |
| 80 | =head1 LIMITATIONS |
| 81 | |
| 82 | bytes::substr() does not work as an lvalue(). |
| 83 | |
| 84 | =head1 SEE ALSO |
| 85 | |
| 86 | L<perluniintro>, L<perlunicode>, L<utf8> |
| 87 | |
| 88 | =cut |